The invention provides a technology for hydrolyzing lignocelluloses biomass into sugar. Hydrolysis is carried out through adding crushed biomass into an acid solution to carry out hydrolysis reaction in water after adsorption through a carbon material, thereby obtaining a sugar solution. The technology has the advantages and beneficial effects that cellulose is efficiently converted into a monosaccharide product through two-step reaction, the reaction conditions are relatively mild, the preparation process of a catalyst is simple and convenient, a carbon-based solid acid catalyst and hydrochloric acid can be recycled for multiple times, and the technology is low in energy consumption and small in pollution and has the potential for large-scale industrial application.